1. Field of the Invention
The present invention relates to pressure relief valves and, more particularly, to a combination pressure relief and shut-off valve.
2. Description of the Prior Art
U.S. Pat. Nos. 4,273,151 and 4,171,004 both disclose safety relief valves having particular suitability for use with beverage dispensing equipment. U.S. Pat. No. 4,171,004 describes a device having a pressure regulator system with a diaphragm actuated stem valve. A reduced pressure chamber is formed between the diaphragm and stem valve which communicates with a combination shut-off valve and pressure relief valve. These operate to relieve excess pressure and prevent such pressure from reaching downstream equipment.
Because the shut-off valve and relief valve are preformed integral portions of one body, no relative adjustment between the two is possible. As such, even though the relief valve may be venting excess pressure, unless such pressure is abrupt or substantial, the shut-off valve will not completely stop flow to downstream equipment. This is a serious disadvantage--particularly with high pressure sources
Also, not only does one preformed body comprise two valves, but gas flow to user equipment is dictated by predetermined passageways through the body. In essence, two valves must be replaced simply to alter gas flow rate or to make repairs or changes to one valve.
U.S. Pat. No. 4,273,151 discloses a safety relief valve whereby inline gas flow is deflected 90.degree. by a baffle toward an offset valve pressure chamber. In this way, the valve will function regardless of direction of gas flow. While the baffle does create a pressure drop and diminish gas flow, no positive inline shut-off valve is provided.